Molecular analysis of CYP1B1 in Omani patients with primarycongenital glaucoma: a pilot study

Stefan El-Gayar,1 Anuradha Ganesh,1 Gabriela Chavarria-Soley,3 Sana Al-Zuhaibi,1 Rayhanah Al-Mjeni,2

Sandy Raeburn,2 Alexander A. Bialasiewicz1

1Department of Ophthalmology, Sultan Qaboos University Hospital, Muscat, Oman; 2Department of Genetics, Sultan QaboosUniversity Hospital, Muscat, Oman; 3Institute of Human Genetics, Friedrich Alexander University, Erlangen, Germany

Purpose: To screen cytochrome P4501B1 (CYP1B1) for causative mutations in Omani patients with a clinical diagnosisof primary congenital glaucoma (PCG)Methods: Nine PCG families were recruited for the study. All patients underwent detailed clinical examinations to confirmthe diagnosis of PCG. The families of index patients were also examined. Genealogical information was obtained bypedigree analysis. The primary candidate gene, CYP1B1, was amplified from genomic DNA, sequenced, and analyzed inpatients to identify the disease-causing mutations.Results: Eight of the nine PCG families were consanguineous (89%). Molecular analysis of CYP1B1 showed three distinctmutations, p.G61E, p.D374N, and p.R368H, in seven of nine unrelated PCG index patients (78%). Six patients hadhomozygous mutations and one had a compound heterozygous mutation. Causative mutations were not identified in twofamilies. In family 4, the index patient was found to be heterozygous for the p.E229K variant. In family 6, although affectedindividuals were found to be homozygous in the CYP1B1 region, no mutation could be identified.Conclusions: This study indicates that CYP1B1 could be the predominant cause of PCG in the Omani population (78%).Omani PCG patients show allelic heterogeneity. Further studies are needed to delineate the spectrum of CYP1B1mutationsin Omani PCG families and to identify new or modifier genes contributing to the manifestations of PCG in this region.

Primary congenital glaucoma (PCG; OMIM 231300;gene symbol, GLC3) is characterized by congenital elevationof intraocular pressure (IOP) consequent to impaired aqueousoutflow via the trabecular meshwork. While uncommon in theWest (less than 1 in 30,000 live births), PCG is relativelycommon in the Middle East with an estimated incidence of 1in 2,500 live births. This is partly attributed to the highincidence of consanguineous marriages in this region [1]. InSaudi Arabia, a neighboring state of Oman, PCG has beenfound to be the predominant cause for childhood blindness[1].

Clinically, PCG is unassociated with other ocular orsystemic diseases and is divided into three subsets, newbornPCG (patients recognized at birth or in the first month of life),infantile PCG (patients presenting in the first two years oflife), and juvenile PCG (patients diagnosed after two years ofage) [2]. More than 80% of the cases present within the firstyear of life with 25% diagnosed in the neonatal period and60% within the first six months of life [3]. In 75% of cases,both eyes are involved, and males are affected somewhat moreoften than females [4].

The disease is characterized by high IOP, buphthalmos,megalocornea, and breaks in Descemet’s membrane with

Correspondence to: Dr. Anuradha Ganesh, M.D., M.R.C.Ophth,Pediatric Ophthalmology Unit, Sultan Qaboos University Hospital,PO-38, PC-123, Muscat, Oman; Phone: 99362501; FAX: 24144560;email: gananu@gmail.com

corneal opacification. PCG in the Middle East is moreaggressive and is associated with poorer therapeutic outcomesthan in the West [5,6].

About 10% of all PCG cases are inherited, the mode ofinheritance being largely autosomal recessive with variablepenetrance. Strong inheritance (vertical transmission) israrely observed in some families and is explained bypseudodominance [7]. Three chromosomal regions, 2p21 atlocus GLC3A [8,9], 1p36 at locus GLC3B [10], and 14q24.3at locus GLC3C [11] have been reported to be associated withPCG. The only identified gene so far is CYP1B1 at locusGLC3A, and this gene encodes for cytochrome P450 1B1 [8,9]. This enzyme is a cell membrane bound monomeric mixed-function oxygenase believed to interact with an arachidonatemetabolite that is important for the normal development andfunction of the anterior segment of the eye [12].

To date, more than 60 mutations associated with PCG anda few polymorphisms in CYP1B1 have been found [13], onethird of them being deletions or insertions, implying aninherited instability of the gene. A total of six common singlenucleotide polymorphisms (SNPs) have been identified in theCYP1B1 region, one upstream of exon 2 (rs2617266) and fivecoding SNPs (rs10012 [p. R48G], rs1056827 [p.A119S],rs1056836 [p.V432L], rs1056837 [p.D449D], and rs1800440[p.N453S]) [11]. These SNPs are embedded in a CYP1B1region in linkage disequilibrium [14].

There is a high incidence of consanguinity in Oman (upto 36%), which leads to a high prevalence of autosomal

Molecular Vision 2009; 15:1325-1331 <http://www.molvis.org/molvis/v15/a140>Received 9 April 2009 | Accepted 5 July 2009 | Published 8 July 2009

© 2009 Molecular Vision

1325

recessive diseases in the country [15]. To date, the geneticbasis and prevalence of various mutations among Omani PCGpatients has not been studied. We report the results of a pilotstudy to determine the distribution of CYP1B1 mutations inOmani patients with PCG.

METHODSThis research was performed in accordance with theDeclaration of Helsinki and with the approval of the MedicalResearch Ethics Committee of the Sultan Qaboos University(Muscat, Oman). The families of nine patients consented toparticipate after being informed of the nature of the research.

PCG patients who were registered in the ocular geneticsdatabase of the Department of Ophthalmology, SQUH, Omanwere recalled. Patients with ocular abnormalities or systemicdiseases suggestive of secondary glaucoma such as aniridia,anterior segment dysgenesis, Lowe syndrome, and Sturge-Weber syndrome were excluded from the study.

All patients were examined by at least one of the authors(A.G., S.E., S.Z., A.B.), either in the office awake or sedated,or underwent an examination under anesthesia. Ophthalmicexamination included evaluation of best-corrected visualacuity (with age-appropriate tests), corneal diameter, IOP(with Tonopen XL or Perkins tonometer), corneal thickness(with ultrasound pachymeter), cup-disc ratio (with indirectophthalmsocopy with +20D), and axial length (withultrasound biometry). IOP values were corrected for cornealthickness based on nomograms. Slit lamp examination,gonioscopy, visual field evaluation (automated visual fieldHumphrey 24–2 or Goldman) and fundus photography weredone when feasible. Glaucoma was diagnosed if patientsdemonstrated an IOP ≥22 mmHg with other signs of PCGincluding buphthalmos, megalocornea, corneal edema,Haab’s striae, and increased cup/disc ratio.

Genealogical information was obtained by pedigreeanalysis. The siblings, parents, and other family memberssuspected to have PCG were clinically examined along withthe proband.

Genomic DNA was extracted from peripheral blood. Thetwo coding exons of CYP1B1 were amplified using fourpreviously published primer pairs [16]. For amplification, atouchdown polymerase chain reaction (PCR) program wasused with annealing temperature decreasing from 65 °C to55 °C over nine cycles followed by 24 cycles with anannealing temperature of 55 °C in a 25 μl mixture (PCRconditions available on request). Sequencing reactions wereperformed on both strands using the BigDye TerminatorCycle Sequencing Kit v3.1 (Applied Biosystems, Foster City,CA) according to the manufacturer’s instructions. Theproducts were analyzed on an ABI Genetic Analyzer 3730(Applied Biosystems). Using segregation analysis in thefamilies, haplotypes were constructed using the six previouslymentioned common SNPs in the gene, one upstream of exon

2 (rs2617266) and five coding SNPs (rs10012 [p. R48G],rs1056827 [p.A119S], rs1056836 [p.V432L], rs1056837[p.D449D], and rs1800440 [p.N453S]) [11]. Mutations whenfound were confirmed in family members.

RESULTSNine patients with PCG (5 males, 4 females) and their familieswere enrolled in the study. All affected patients had IOPsgreater than or equal to 21 mmHg as well as increased cornealdiameters (>12mm), cup-disc ratios, and axial lengths. Allpatients included in the present study had an aggressive formof glaucoma with onset within the first month of life and hadundergone multiple surgical interventions for control of theirglaucoma. The clinical data are summarized in Table 1 andTable 2.

Consanguinity was found in eight of the nine families(89%) without any gender preference (Table 3). In fivefamilies, more than one individual was affected. Thepresumed mode of inheritance according to pedigree analysiswas autosomal recessive in all families. Molecular analysis ofCYP1B1 permitted the identification of three causativemutations in seven of the nine index cases (78%; Table 3).The p.G61E, p.D374N, and p.R368H mutations have all beenpreviously reported as disease-causing mutations [1,17]. Theidentified mutations were homozygous in six patients andcompound heterozygous in one patient (Table 3). Themutations segregated with the disease in the seven families.The index case in family 4 presented the previously reportedrisk-associated but not clearly disease-causing [18] p.E229Kvariant in heterozygous form. Haplotype analysis for family4 using the six coding SNPs in CYP1B1 ruled out this variantas the cause of PCG (Figure 1A). It did not segregate with thedisease since the affected brother of the index patient (II.1)did not carry the variant. No mutation in CYP1B1 could beidentified for family 6 (Table 3). Haplotype analysis,however, suggested linkage to the CYP1B1 locus, GLC3A(Figure 1B). Both affected individuals (II.2 and II.3) werehomozygous for the same SNP haplotype, 5′-CCGGTA-3′,while their unaffected sister was heterozygous. Thus, a totalof 14 mutations and one risk-associated variant were found inthe nine patients representing an overall mutation rate of 14in 18 (78%) studied chromosomes.

DISCUSSIONPCG is a genetically heterogeneous disorder that maps to atleast three different loci. However, in the majority of PCGpatients, the candidate locus has been found to be GLC3A,which codes for a cytochrome p450 protein called CYP1B1[9]. Among patients with PCG, the proportion of patients dueto CYP1B1 mutations is variable across populations from~100% among Saudi Arabians [1,17] and Slovakgypsies(Roms) [19] to ~20% in Japanese [20]. We detected threedistinct disease-causing CYP1B1 mutations in seven of the

Molecular Vision 2009; 15:1325-1331 <http://www.molvis.org/molvis/v15/a140> © 2009 Molecular Vision

1326

TAB

LE 1

. CLI

NIC

AL

DET

AIL

S IN

STU

DY

PATI

ENTS

WIT

H PR

IMA

RY

CO

NG

ENIT

AL

GLA

UC

OM

A I.

Prob

and

Age

of

onse

tA

ge a

tD

xC

urre

ntag

e

Cor

neal

Dia

met

erV

,H [m

m]

Cor

neal

Haz

e O

D/

OS

IOP

[mm

Hg]

OD

/OS

at D

x

IOP

[mm

Hg]

OD

/OS

Cur

rent

cIO

P[m

mH

g]O

D/O

S

Gon

iosc

opy

OD

/OS

[Sha

ffer

]or

AC

dept

h

Axi

alL

engt

h[m

m]

OD

/OS

Ref

ract

ion

[Sph

eric

Equ

ival

ent]

OD

/O

S

Cup

-Dis

cR

atio

OD

/O

S

Vis

ual

Acu

ity[D

ecim

al]

OD

/OS

Tre

atm

ent

Fam

ily 1

prob

and

at b

irth

at b

irth

10 y

12,1

2/12

,12

mild

/ mild

ND

19/2

318

/22

1–2/

1–2

22.7

4/25

.17

−1.5/-9.7

50.

4/0.

81.

0/0.

2O

U T

rab

(7d)

;LE

ALT

+Tra

b(3

y); O

UM

edic

atio

nsFa

mily

2pr

oban

dat

birt

h“l

ate”

24 y

14,1

4/13

,13

clea

r/ cl

ear

ND

45/4

546

/43

3.5

h op

en,

PAS/

open

25.2

3/24

.04

−3.75/.4.2

51.

0/0.

9H

M/0

.1O

S M

edic

atio

nsO

SA

ffec

ted

sibl

ing

at b

irth

7 y

13 y

11,1

2/12

,15

clea

r/se

vere

ND

18/ d

igita

lly so

ft18

2/de

ep A

CN

D/ N

D−1.37/N

A0.

7/N

A0.

1/N

LPO

D T

rab

+MM

C (7

y);

OS

no R

x.; O

DM

edic

atio

nsA

ffec

ted

sibl

ing

at b

irth

5 y

11 y

13,1

5/N

Dm

ild/N

AN

D21

/NA

281/

NA

22.5

3/N

A+0

.5/N

A0.

8/N

D0.

5/N

AO

D T

rab

(5y)

;O

S en

ucle

atio

n(9

y); O

DM

edic

atio

nsFa

mily

3pr

oban

dat

birt

h5

d11

y12

.5,1

2.5

/12

,12

mild

/ cl

ear

ND

21 /1

310

/08

norm

al A

C/

norm

al A

C23

.05/

20.9

20.

0/+0

.50.

3/0.

40.

05/0

.5O

D T

rab

(2w

)(´

3); O

S Tr

ab(2

w) (

´2);

OU

Med

icat

ions

Fam

ily 4

prob

and

uncl

ear

uncl

ea r23

y12

.5,1

2.5/

11.

5,12

.0cl

ear/

clea

r>5

0/>5

017

/15

19/1

63/

3N

D/ N

D−3.37/-2.8

70.

8/0.

90.

3/0.

6O

U T

rab

(6y)

;O

UM

edic

atio

nsA

ffec

ted

sibl

ing

at b

irth

at b

irth

3 y

12.5

,13/

12.

5,12

.5; a

t14

m:

11,1

1.5/

11,

11.5

clea

r/ cl

ear

>50/

>50

12/1

87/

14N

D/N

D21

.09/

20.3

4, a

t14

m:

19.9

2/19

.67

−1.75/-2.0

0.0/

0.0

0.5/

0.5

OU

Tra

b+Tr

ab(3

y); N

om

edic

atio

ns

Fam

ily 5

prob

and

at b

irth

at b

irth

3 y

11,1

2/N

D;

at b

irth:

10,1

0/12

,12

clea

r / N

A38

/ 36

22 /

NA

18no

rmal

AC

/N

A19

.7/

NA

, at

birth

:18

.47/

19.2

7

−5.75/N

A0.

1/N

Asc

0.0

5/N

LPO

D T

rab

+ Tr

ab(3

w);

OS

Trab

+le

nsec

tom

y+a

nter

ior

vitre

ctom

y(3

w);

No

med

icat

ions

Fam

ily 6

prob

and

at b

irth

at b

irth

3 y

11.5

/12

>30/

3030

/25

39/1

80.

4/0.

50.

05/0

.15

(low

coo

p.)

OU

Tra

b; N

om

edic

atio

nsA

ffec

ted

sibl

ing

at b

irth

at b

irth

6 m

11.5

,11.

0/1

0,10

clea

r / c

lear

ND

norm

al A

C/

norm

al A

C18

.64/

18.6

3−0.62/-1.3

70.

5/0.

9fo

llow

slig

ht/

follo

ws

light

Med

icat

ions

only

; Aw

aitin

gSx

Molecular Vision 2009; 15:1325-1331 <http://www.molvis.org/molvis/v15/a140> © 2009 Molecular Vision

1327

TAB

LE 1

. DA

TA C

ON

TIN

UED

.

Prob

and

Age

of

onse

tA

ge a

tD

xC

urre

ntag

e

Cor

neal

Dia

met

erV

,H [m

m]

Cor

neal

Haz

e O

D/

OS

IOP

[mm

Hg]

OD

/OS

at D

x

IOP

[mm

Hg]

OD

/OS

Cur

rent

cIO

P[m

mH

g]O

D/O

S

Gon

iosc

opy

OD

/OS

[Sha

ffer

]or

AC

dept

h

Axi

alL

engt

h[m

m]

OD

/OS

Ref

ract

ion

[Sph

eric

Equ

ival

ent]

OD

/O

S

Cup

-Dis

cR

atio

OD

/O

S

Vis

ual

Acu

ity[D

ecim

al]

OD

/OS

Tre

atm

ent

Fam

ily 7

prob

and

at b

irth

at b

irth

20 y

8,9/

9,11

seve

re/

seve

re, a

tbi

rth: B

E“w

hite

corn

ea”

ND

NA

/NA

NA

/NA

NA

/NA

NA

/NA

NA

/NA

NLP

/NLP

OU

Tra

b (9

d)(x

1) (5

y); N

om

edic

atio

ns

Aff

ecte

dsi

blin

gat

birt

hat

birt

h18

y-,1

7/-,1

7se

vere

/se

vere

, at

birth

: BE

“whi

teco

rnea

”

ND

BE

digi

tally

hard

NA

/NA

>30/

>30

NA

/NA

NA

/NA

LP/L

PO

U T

rab

(3–

4y);

No

med

icat

ions

Aff

ecte

dsi

blin

gat

birt

hat

birt

h8

y-,1

4.5/

-,14

.5se

vere

/se

vere

, at

birth

: BE

“whi

teco

rnea

”

ND

BE

digi

tally

hard

deep

AC

/de

ep A

C≈2

7/ ≈

25N

A/N

AN

A/N

ALP

/LP

OU

Tra

b (3

–4m

); N

om

edic

atio

ns

Fam

ily 8

prob

and

uncl

ear

12 y

26 y

12.5

,12.

5/1

2,12

mild

/cle

arN

D45

/16

39/1

8de

ep A

C/

deep

AC

27.8

8/25

.57

−11.

9/-1

.68

NA

/1.0

LP/H

MO

S Tr

ab (2

2y);

No

med

icat

ions

Aff

ecte

dsi

blin

g<

1 y

1 y

23 y

14,1

4/13

.5,

14.5

clea

r / m

ildN

D26

/21

17/1

5no

rmal

AC

/no

rmal

AC

29.1

0/22

.36

≈-6.

5/N

A0.

9/N

A0.

075/

NLP

OS

Trab

(1ye

ar);

No

med

icat

ions

Aff

ecte

dsi

blin

gat

birt

hat

birt

h18

y12

.5,1

2.5/

13,

13se

vere

/se

vere

ND

digi

tally

soft/

digi

tally

har

dN

A/N

A≈1

3/ ≈

25N

A/N

AN

A/N

AN

LP/N

LPO

U T

rab

(20d

);

Fam

ily 9

prob

and

1 m

1 m

17 y

10,1

0/19

,19

seve

re/

seve

reN

DB

E di

gita

lly so

ftN

A/N

A≈2

1/ ≈

29N

A/N

AN

A/N

AN

LP/N

LPO

S Tr

ab (x

7);

No

med

icat

ions

All

data

refe

r to

time o

f las

t exa

min

atio

n ex

cept

whe

re st

ated

diff

eren

tly. A

LT –

argo

n la

ser t

rabe

culo

plas

ty, d

: day

(s),

Cur

r.: cu

rren

t, D

x: d

iagn

osis

, cIO

P: p

achy

met

ryco

rrec

ted

intra

ocul

ar p

ress

ure,

H: h

oriz

onta

l, H

M: h

and

mov

emen

ts, I

OP:

intra

ocul

ar p

ress

ure,

LP:

ligh

t per

cept

ion,

m: m

onth

(s),

MM

C: m

itom

icin

C, N

LP: n

olig

ht p

erce

ptio

n, w

: wee

k(s)

, NA

: not

appl

icab

le, N

D: n

o da

ta av

aila

ble,

OD

: rig

ht ey

e, O

S: le

ft ey

e, O

U: b

oth

eyes

, PA

S: p

erip

hera

l ant

erio

r syn

echi

a, R

x: T

reat

men

t,Sx

: sur

gery

, Tra

b –

Trab

ecul

ecto

my,

Tra

b+tra

b: T

rabe

cule

ctom

y +

Trab

ecul

otom

y, V

-ver

tical

, y: y

ear(

s).

Molecular Vision 2009; 15:1325-1331 <http://www.molvis.org/molvis/v15/a140> © 2009 Molecular Vision

1328

nine PCG index patients (78%). Our results indicate thatCYP1B1 mutations play a crucial role in Omani PCG patientsas in other Arab populations.

The worldwide profile of variations in the coding regionof CYP1B1 in patients with PCG thus far reported isheterogeneous and includes ~70 alterations (Human GenomeMutation Database) [21]. However, the Slovakgypsies(Roms) and Saudi Arabian patients with PCG exhibit allelichomogeneity that has largely been attributed to consanguinityand inbreeding [17,19]. The detection of three disease-causingmutations in seven index cases indicates that Omani PCGpatients show allelic heterogeneity. The three mutations wefound in Omani patients (p.R368H, p.D374N, and p.G61E)have been reported as the most common mutations in theSaudi population, accounting for 72%, 12%, and 7% of thetested alleles, respectively [1,17]. Oman has been a majorgateway in human history with evidence of clear contacts withsub-Saharan West Africa, East Africa (Zanzibar/Mombasa),Iraq, Iran, Pakistan, and India and is expected to have a richgenetic legacy. The degree of heterogeneity within differentpopulations as well as the distribution of mutations have beenseen to be very variable and are believed to be attributable tovariations in gene pools among the different populations[22].

Among the seven index cases with CYP1B1 mutations,one carried two different mutations (compoundheterozygous). The large proportion of Omani PCG patients(6/7; 86%) carrying homozygous mutations in CYP1B1 isindicative of extensive consanguineous marriages in theOmani population.

The p.E229K variant found in family 4 did not segregatewith the disease (Table 3, Figure 1A). Haplotype analysissuggested that mutations in a locus different than GLC3Acould be responsible for PCG in this family. In family 6,(Table 3, Figure 1B) no mutation could be identified.However, both affected individuals were homozygous in theCYP1B1 region, making it likely that a mutation in thepromoter or in some other regulatory region of the gene isresponsible for the disease. Further work with family 4(performing a linkage analysis after recruiting additionalaffected and healthy family members) and family 6 (analysisof cDNA in the affected family members) is in progress.

Our study is the first report of molecular genetic analysisof PCG in the Omani population. To verify the results of thispilot study, to further delineate the role of CYP1B1 mutationsin the pathogenesis of PCG in the Omani population, and toidentify new or modifier genes contributing to themanifestations of PCG in this region, further studies with a

TABLE 2. CLINICAL DETAILS IN STUDY PATIENTS WITH PRIMARY CONGENITAL GLAUCOMA II.

Clinical Parameter Data Range (n=18 PCG patients)Age of onset at birth–1 month*Age at diagnosis at birth–12 yearsAge currently 6 months–26 yearsCorneal diameter horizontally [mm] 9–19Intraocular pressure [mmHg] 12–45Cup-disk ratio 0.0–1.0Axial length [mm] 18.47->30 (and phthisis bulbi in some cases)Pachymetry central [µm] 465–816Refraction as spherical equivalent [D] +0.5 to −11.9Visual acuity [decimal] No Light Perception–1.0

All data refer to time of last examination except where stated differently. The asterisk denotes that in two PCG patients, the ageof onset was unclear (but definitely within one year of age). PCG-primary congenital glaucoma.

TABLE 3. CYP1B1 MUTATIONS ASSOCIATED WITH PRIMARY CONGENITAL GLAUCOMA IN OMANI PATIENTS.

Familynumber Consanguinity Number of affected individuals Gender

MutationsExonAllele 1 Allele 2

1 No 1 Male p.R368H p.R368H III2 Yes 4 Female p.D374N p.D374N III3 Yes 1 Female p.G61E p.G61E II4 Yes 2 Female p.E229K no mutation II5 Yes 1 Male p.G61E p.R368H II/III6 Yes 2 Male no mutation no mutation7 Yes 3 Male p.D374N p.D374N III8 Yes 4 Female p.G61E p.G61E II9 Yes 1 Male p.R368H p.R368H III

Consanguinity was found in eight of the nine families (89%). In five families, more than one individual was affected. Molecularanalysis of CYP1B1 permitted the identification of three causative mutations in seven of the nine index cases (78%).

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larger sample of patients are being planned. Identifying themutation spectrum of CYP1B1 that causes PCG in the Omanipopulation has implications in devising molecular diagnosticsfor rapid screening in predisposed families that would aid inearly intervention.

ACKNOWLEDGMENTSThis study was supported by grants from the MREC (SultanQaboos University, Oman; MREC 229) and the DeutscheForschungsgemeinschaft, SonderforschungsbereichGlaukome (SFB 539). We are grateful to Professor André Reis(Institute of Human Genetics, Friedrich AlexanderUniversity, Erlangen, Germany) for the molecular geneticanalyses. We thank the patients and their families for theirparticipation in the study.

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Figure 1. Pedigree with haplotypes of family 4 (heterozygous mutation). A: Pedigree with haplotypes of family 4 (heterozygous mutation) isshown. In this family, the index patient (II.2) is heterozygous for the E229K mutation as is her unaffected dizygotic twin (II.3) and parents(I.1 and I.2). On the other hand, the index patient’s brother (II.1) does not carry the E229K mutation but has the disease. This suggests thatthe E229K mutation cannot be causative for PCG in this family. The order of the SNPs from top to bottom is rs2617266, rs10012 (p. R48G),rs1056827 (p.A119S), rs1056836 (p.V432L), rs1056837 (p.D449D), and rs1800440 (p.N453S). B: Pedigree with haplotypes of Family 6 (nomutation) is shown. In this family, no CYP1B1 mutation was identified. Analysis of the six known SNPs in CYP1B1 revealed homozygosityfor the 5′-CCGGTA-3′ haplotype in both PCG-affected brothers (II.2 and II.3) and heterozygosity in the unaffected sister (II.1) and parents(I.2 and I.3). This indicates a critical role for the 5′-CCGGTA-3′ haplotype in PCG. The order of the SNPs from top to bottom is:rs2617266, rs10012 (p. R48G), rs1056827 (p.A119S), rs1056836 (p.V432L), rs1056837 (p.D449D), and rs1800440 (p.N453S).

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The print version of this article was created on 5 July 2009. This reflects all typographical corrections and errata to the articlethrough that date. Details of any changes may be found in the online version of the article.

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